JP4538949B2 - Substrate manufacturing method for mounting optical components - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical component mounting substrate on which an optical component is mounted, a mounting substrate in which an optical component or the like is mounted on the optical component mounting substrate, and a printed circuit board in which the mounting substrate is bonded via conductive bumps.
[0002]
[Prior art]
In order to make a computer that can perform arithmetic processing faster, the clock frequency of the CPU tends to increase more and more, and now the one of the order of 1 GHz has appeared. As a result, there is a portion where high-frequency current flows in the copper electrical wiring on the printed circuit board in the computer, so that malfunctions may occur due to the generation of noise, and electromagnetic waves may be generated, adversely affecting the surroundings. It will also be.
[0003]
In order to solve such problems, a part of the electrical wiring made of copper on the printed circuit board is replaced with an optical fiber or an optical waveguide (hereinafter referred to as an optical wiring), and an optical signal is used instead of the electrical signal. ing. This is because the generation of noise and electromagnetic waves can be suppressed in the case of optical signals.
[0004]
Generally, like an IC or the like, a photoelectric element such as a laser diode (LD) or a photodiode (PD) is mounted on a substrate surface, and signal transmission is performed on the substrate surface by a waveguide. In such an optical circuit, when the number of electrical components such as ICs increases, it is necessary to cross the optical waveguide, and there is a problem that the optical axis alignment between the optical waveguide and the photoelectric element becomes increasingly difficult. .
[0005]
More specifically, along with the practical application of optical communication systems through the development of low-loss optical fibers, development of various optical communication components is desired. And establishment of the optical wiring technique which mounts these optical components in high density, especially an optical waveguide technique is desired. In general, optical waveguides are required to satisfy the following conditions: (1) small optical loss, (2) easy manufacture, and (3) control of refractive index difference between core and clad. So far, quartz-based optical waveguides have been mainly studied as low-loss optical waveguides. As demonstrated by optical fibers, quartz has extremely good light transmission, so that a loss of 0.1 dB / cm or less is achieved even when a waveguide is used, and even when the wavelength is 1.3 μm. However, quartz has poor flexibility and needs to be produced on a silicon substrate or the like. If it is mounted on a printed circuit board as it is, there is a problem that connection of electric parts is greatly restricted.
[0006]
On the other hand, in recent years, an optical waveguide using a polymer among the optical waveguides has attracted attention because it may be manufactured at a low cost by a simple process. As an example, plastic optical waveguides such as polymethyl methacrylate (PMMA), polystyrene (PS), and polycarbonate (PC) achieve sufficiently low optical loss in the wavelength region longer than the visible wavelength compared to quartz optical waveguides. Although there are drawbacks such as not being performed, formation at a low temperature is possible and processing is easy. In the manufacturing method, a clad made of a low refractive index polymer material and a core layer made of a high refractive index polymer material are sequentially formed on a base material such as a silicon substrate, and a dry etching process is performed using the photoresist pattern as a mask. After the polymer core layer having a substantially rectangular cross section is processed in this way, a clad layer is formed on the upper portion again with a low refractive index polymer material to form an optical waveguide having a total film thickness of 30 to 60 μm.
[0007]
After the above process, the optical waveguide is peeled off from a base material such as silicon using hydrofluoric acid or the like, and bonded to the electric wiring board using an adhesive to produce an optical component mounting substrate.
[0008]
However, once the polymer optical waveguide is peeled off from a silicon substrate or the like to form a film, shrinkage occurs due to a difference in thermal expansion coefficient, and sufficient bonding accuracy to the electric wiring board cannot be obtained. In some cases, the refractive index fluctuates with a problem such as a crack due to a shrinkage factor, causing optical loss of the optical waveguide, and has not yet been put into practical use. In addition, the accuracy in the vertical direction when pasting to the electric wiring board is strict, and the same ± 1 μm or less as that of the optical component mounting is required, and the pasting is accompanied with great difficulty.
[0009]
In addition, the progress in technology for miniaturization and high performance of semiconductor chips is remarkable, and in order to efficiently mount surface mount parts such as optical parts and electrical parts, there is a demand for further lighter, thinner and shorter equipment. It is also required to realize finer wiring than ever before on the top of the combined optical waveguide.
[0010]
[Problems to be solved by the invention]
The present invention has been made in view of the state of the related art, and enables high-density mounting of an electrical component or an optical component on an optical waveguide, and easily realizes optical axis alignment between the optical waveguide and the photoelectric element. An object of the present invention is to provide an optical component mounting substrate, a mounting substrate, and a printed board.
[0011]
In one embodiment of the present invention, a process for forming a via hole penetrating the photosensitive glass substrate by exposing a via hole forming portion of the photosensitive glass substrate by ultraviolet irradiation and performing a heat treatment and a development treatment by an acid treatment. And filling the via hole with a resin to smooth the first surface of the photosensitive glass substrate and the second surface opposite to the first surface, and the via hole filled with the resin. applying a first optical wiring material on the first surface of the photosensitive glass substrate, patterning the first optical wiring material to form a first optical wiring layer having a core and a cladding, the first forming a first optical path conversion mirror for coupling the core of the optical component and the first optical wiring layer optically to the first optical wiring layer, the via hole is filling with the resin A step of applying a second optical wiring material on the second surface facing the first surface and the first optical wiring material is applied of the photosensitive glass substrate, patterning the second optical wiring material, the core And forming a second optical wiring layer having a cladding and a second optical path conversion mirror for optically coupling the second optical component and the core of the second optical wiring layer in the second optical wiring layer Forming , heating the photosensitive glass substrate on which the first optical wiring layer and the second optical wiring layer are formed, pyrolyzing the resin filled in the via hole, and the first light the wiring layer and the second optical wiring layer, forming a through hole at a position corresponding to the via hole, Rutotomoni to deposit the conductor in said via hole and the through-holes by plating, the photosensitive glass substrate Formed on the first surface By sufficiently growing the plating so as to protrude from both the surface of one optical wiring layer and the surface of the second optical wiring layer formed on the second surface of the photosensitive glass substrate, A pad connected to the first optical component is formed on the surface of the first optical wiring layer, or a pad connected to the second optical component is formed on the surface of the second optical wiring layer. And a step of forming bumps on the surface of the optical wiring layer .
The photosensitive glass substrate preferably contains at least one material selected from the group consisting of Au and CeO2.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an optical component mounting board, a mounting board, and a printed board according to the present invention. The optical component mounting substrate 10 of the present invention has at least an optical wiring layer 9 composed of an optical component mounting portion, a core, and a clad on one or both surfaces of the glass substrate 1, and is electrically connected to the optical component mounting portion. A via hole penetrating the substrate is provided. Further, an optical component 14 and an electrical component 15 are mounted thereon to form a mounting board. The mounting board (optical component mounting board 10) is connected to the printed board 20 shown on the lower side in the figure.
[0013]
More specifically, the optical component mounting substrate 10 uses the glass substrate 1 as a base material. At least one optical component mounting portion (pad, electrical wiring, etc.) and an optical wiring layer composed of a core and a cladding are formed on at least one surface of the glass substrate. Further, the glass substrate 1 is provided with a through hole 2. The inside of each hole 2 is filled with a conductor provided by plating, and a bump corresponding to the position of the electrode 21 of the printed wiring 20 is provided below. Thereby, the optical component, the electrical component, and the electrode on the printed wiring board 20 side can be electrically connected.
[0014]
By adopting this configuration, the process of peeling the optical waveguide to form a film is unnecessary, and the positional accuracy with respect to the electric wiring board is also improved.
[0015]
Next, a manufacturing method of the optical component mounting substrate 10 shown in FIG. 1 will be described. 2 to 9 are process diagrams showing the manufacturing process of the optical component mounting board 10. The optical component mounting portion forming surface (electrical wiring layer) and the optical wiring layer forming surface in the description are referred to as b-plane and the bumps as a-plane.
[0016]
The glass substrate 1 is preferably a photosensitive glass plate having a chemical workability of Li ₂ O—Al ₂ O ₃ —SiO ₂ (Au, CeO ₂ ) system. Further, the a and b surfaces of the glass substrate 1 have excellent smoothness. The glass substrate was irradiated with 100 mJ / cm ^{2 of} a Hg—Xe lamp through a photomask having a hole shape (see FIG. 2) and developed. When the components Au and CeO ₂ in the photosensitive glass are exposed by ultraviolet irradiation, nuclei composed of particles of the photosensitive metal Au and CeO ₂ are formed in the exposed portion to form a latent image (not shown). it can.
[0017]
Thereafter, the glass on which the latent image has been formed by exposure is heat-treated at 550 ° C. to 620 ° C., thereby precipitating crystals that easily elute into the acid. By this heat treatment, lithium metasilicate crystals are precipitated with the photosensitive metal particles present in the exposed portion (latent image) as nuclei. The crystals thus obtained have a property of being easily dissolved in an acid, and thus were subjected to an acid treatment with dilute hydrofluoric acid and a development treatment (see FIG. 3).
[0018]
As a result of the above process, a via hole 2 is formed in the photosensitive glass substrate 1. The via hole is a hole that penetrates the photosensitive glass substrate 1 and is formed so as to coincide with the position of the electrode on the printed circuit board 20 side to be connected.
[0019]
The surface b of the photosensitive glass substrate 1 on which the via hole 2 is formed is filled with the via hole 2 with light or thermosetting resin 3 to make the surface b of the glass substrate 1 smooth, and then an optical wiring layer material ( The lower clad 4 and the core 5 are sequentially applied with polyimide, for example (see FIG. 4).
[0020]
Next, a photoresist 6 is applied to the upper portion of the optical waveguide material (see FIG. 5), exposed with a waveguide pattern mask, the photoresist 6 is developed, and the exposed portion is removed. Then, the core is patterned so that the cross section becomes rectangular by reactive ion etching, and then the photoresist 5 is removed.
[0021]
The core is formed to have at least one of a straight line, a curved line, an S-shaped curve, a parallel line, and the like.
[0022]
Further, the mirror 7 is formed at a predetermined portion of the core wiring pattern, and the upper clad 8 is applied again to form the optical wiring layer 9 (see FIGS. 6 and 7). The mirror 7 processes the core at an angle of 45 ° with a laser or the like, and selectively deposits an Al film. At this time, an alignment mark 23 for mounting an optical component is formed in an arbitrary position on the lower clad with an Al film.
[0023]
Thereafter, a heat treatment process of the optical wiring layer is performed at about 350.degree. The resin filled in the via hole 2 is thermally decomposed and removed here. When the decomposition component of the resin remains in the hole, the organic residue can be removed with dichromic acid, permanganic acid or the like.
[0024]
Then, a conductor is deposited in the via hole 2 by plating, and the bump 11 is formed by sufficiently growing the plating so as to protrude from the surface of the photosensitive glass substrate 1a (see FIG. 8).
[0025]
When plating is performed, a low-viscosity adhesive layer is selectively applied only to the inner wall surface of the via hole 2, and a plating process is performed on the adhesive layer, so that the adhesion between the photosensitive glass interface and the plated metal film is achieved. Can be further improved. Thus, the via hole 2 is filled with the metal conductor, and the bump 11 is formed on the a-plane side.
[0026]
The optical wiring layer is additionally processed in a blind via shape by laser irradiation or the like so as to match the position of the via hole 2 of the photosensitive glass substrate 1, and the via hole 2 is also formed on the optical wiring layer side (see FIG. 9). . Similarly, the inside is filled with a metal conductor by plating, and a pad is formed on the surface of the optical wiring layer 9 with the metal conductor.
[0027]
An optical element (LD, PD), LSI chip, and the like on the optical component mounting substrate 10 manufactured as described above are relied on the alignment mark formed in the lower clad simultaneously with the mirror process so that the optical axis is not shifted. To be installed. Since the photosensitive glass substrate 1 has a smooth surface, the distance in the height direction from the alignment mark can be accurately grasped, so that the optical component is installed on the end face of the optical component mounting substrate 10 so that the optical axis is not shifted. Is also possible. Thereafter, the optical component mounting board 10 itself is connected to the printed board to complete the first example of FIG.
[0028]
Optical components such as PD / LD and electrical components such as LSI are connected to the wiring pattern on the optical component mounting board via lead wires or bumps. On the other hand, electrodes 21 for electrical connection with the bumps 11 of the optical component mounting substrate 10 are provided on the upper surface of the printed circuit board 20 and are connected to each other. As a result, optical components such as PD and LD and electrical components such as LSI and the printed circuit board 20 are electrically connected.
[0029]
Further, a part of the electrical signal from the printed circuit board 20 is converted into an optical signal by the LD, and the optical signal is incident on the waveguide. Then, the optical signal is reflected by the mirror and transmitted through the optical waveguide, reflected again by the mirror, converted into an electric signal by the PD, and signal processing is performed by an LSI or the like. Thus, electrical connection and optical connection can be realized with high reliability. A plurality of such optical component mounting boards may be mounted on a printed circuit board to enhance the optical communication device and the optical information device.
[0030]
FIG. 10 is a diagram showing a second example of a printed circuit board on which the optical component mounting board of the present invention is mounted. This is an example in the case where the electrical wiring layer 22 is formed on the optical wiring layer of the photoelectric wiring board to form a multilayer structure.
[0031]
In the optical component mounting substrate 10 shown in this example, the via hole 2 of the photosensitive glass substrate 1 is filled with a conductive material, and the wiring electrode of the optical wiring layer and the wiring electrode of the electric wiring layer on the optical wiring layer are optical components or The electrical wiring density is made to correspond to the electrode of the electrical component and connected to the via hole 2.
[0032]
On the other hand, the position of the bump 11 from the via hole 2 formed on the photosensitive glass substrate a surface side is a position to be matched with the electrode 21 of the printed circuit board 20.
[0033]
In this way, optical elements (LD, PD), LSI (bare) chips and the like are mounted on the top using the manufactured opto-electric wiring 10, and the optical component mounting board is connected to the printed board. In this way, a part of the electrical signal from the printed circuit board 20 is converted into an optical signal by the LD, and the optical signal reflected by the mirror is transmitted through the optical waveguide. The optically transmitted signal is again converted by a mirror by 90 °, converted to an electric signal by a PD, and processed by an LSI or the like. Thus, electrical connection and optical connection can be realized with high reliability.
[0034]
Next, a method for manufacturing the optical component mounting substrate 10 shown in FIG. 11 will be described. 12 to 14 are process diagrams showing the manufacturing process of the optical component mounting board 10. In the description, the lower bump forming surface is a-plane, and the opposite surface (upper surface) is b-plane.
[0035]
The process of forming the optical wiring layer on one surface of the photosensitive glass substrate is the same as the manufacturing method of the optical component mounting substrate 10 shown in FIGS. Subsequently, the lower clad 4, the core 5, and the upper clad 8 are sequentially applied to the a-plane side of the glass substrate 1 with an optical wiring material (for example, polyimide) in exactly the same procedure to form an optical wiring layer 9. The core 5 is patterned so as to have a rectangular cross section, and a mirror 7 is provided at a predetermined portion of the core wiring pattern (see FIG. 12).
[0036]
A blind via is additionally processed with a laser or the like so that at least one of the optical wiring layer 9 on the a-plane or b-plane matches the position of the via-hole 2 on the photosensitive glass substrate 1, and the via-hole 2 is also formed in the optical wiring layer. (See FIG. 13). Further, the metal conductor is filled by plating, and the bump 11 is formed by sufficiently growing the plating so as to protrude from the surface of the optical wiring layer 9. Also, metal conductors are wired on the upper and lower surfaces of the optical wiring layer 9.
[0037]
Optical elements (LD, PD), LSI chips, etc. on both sides of the optical component mounting substrate 10 manufactured as described above, the optical axis does not shift by relying on alignment marks etc. formed in the lower cladding simultaneously with the mirror process. The mounting board is manufactured by mounting as described above. Since the photosensitive glass substrate 1 has a smooth surface, the cladding layer and alignment marks applied on the upper surface remain smooth. Therefore, the alignment accuracy when the optical component 14 is mounted can be maintained high, and the optical axis shift can be suppressed. In addition, since the distance (film thickness) in the height direction can be accurately grasped, it is possible to install the optical component 14 on the end face of the optical / electrical wiring board 10 so that the optical axis does not shift. Thereafter, the mounting board itself is connected to the printed board to complete the example of FIG.
[0038]
In the optical component mounting substrate and printed circuit board produced as described above, optical components such as PD / LD and electrical components such as LSI are connected to the wiring pattern and via hole on the optical component mounting substrate via lead wires or bumps. On the other hand, electrodes 21 are provided on the upper surface of the printed circuit board 20 to be electrically connected to the bumps 11 protruding from the via holes of the optical component mounting board 10 and are connected to each other. As a result, optical components such as PD and LD and electrical components such as LSI and the printed circuit board 20 are electrically connected.
[0039]
Further, a part of the electrical signal from the printed circuit board 20 is converted into an optical signal by the LD, and the optical signal is incident on the waveguide. Then, the optical signal is reflected by the mirror and transmitted through the optical waveguide, is again mirror-reflected and becomes an electric signal by the PD, and signal processing is performed by the LSI or the like. Thus, electrical connection and optical connection can be realized with high reliability. A plurality of such optical / electrical wiring boards having a size ranging from several centimeters to several tens of centimeters may be mounted on a printed circuit board to enhance the optical communication device and the optical information device.
[0040]
FIG. 15 is a diagram showing a second example of a printed circuit board on which the optical component mounting board of the present invention is mounted. This is an example in the case where the electrical wiring layer 22 is formed on both sides of the optical wiring layer of the optical component mounting substrate to form a multilayer structure. Here, the electrical wiring layer 22 can be formed using a known additive method or subtract method.
[0041]
In the optical component mounting substrate 10 shown in this example, the via hole 2 of the photosensitive glass substrate 1 is filled with a conductive material, and the wiring electrode 16 of the optical wiring layer and the wiring electrode 16 of the upper electric wiring layer are formed. It has a wiring density corresponding to the electrodes of optical components and electrical components and is connected to the via hole 2.
[0042]
On the other hand, the position of the via hole 2 on the photosensitive glass a surface side is a position to be matched with the electrode 21 of the printed circuit board 20, and the via hole 2 and the electrode 21 are connected. In this way, the optical wiring layer and the electrical wiring layer can be formed in multiple layers on the glass substrate as the main components, so that the electrical wiring density can be made to correspond to the electrodes of the optical components and electrical components mounted on the top, Efficient device mounting becomes possible.
[0043]
The optical element (LD, PD), LSI (bare) chip, and the like are mounted on the top using the optical component mounting substrate 10 thus manufactured, and the optical / electrical wiring substrate is connected to the printed circuit board. In this way, a part of the electrical signal from the printed circuit board 20 is converted into an optical signal by the LD, and the optical signal reflected by the mirror is transmitted through the optical waveguide. The optically transmitted signal is again converted by a mirror by 90 °, converted to an electric signal by a PD, and processed by an LSI or the like. Thus, electrical connection and optical connection can be realized with high reliability.
[0044]
Incidentally, in the optical waveguide, quartz, polycarbonate, polymethyl methacrylate, or a polymeric material composed of polystyrene, or _{SiO 2 - Ge 2, ZrF 4} - BaF 2 - GdF 3 - AlF 3, As- S, As- Even if it is configured using either a glass system made of Ge-Se or the like or a crystal system made of CsBr, KRS-5, or the like, the structure shown in FIG.
[0045]
【The invention's effect】
The optical component mounting substrate of the present invention forms an optical wiring layer wired directly on a glass substrate. Therefore, the optical axis alignment between the optical component and the optical wiring layer is highly accurate. Further, since the optical wiring layer (waveguide film) is not peeled off, there is no change in various physical properties such as refractive index due to shrinkage. Furthermore, if the optical component mounting portion is an electrical wiring layer, it is possible to provide a mounting substrate that corresponds to the electrical wiring density of the optical component mounted on the optical component mounting portion and the electrodes of the electrical component, and via holes and conductive bumps can be provided. It can be connected to a printed circuit board with low wiring density via
[0046]
As described above, the connection characteristics and reliability of the optical waveguide as the transmission line are remarkably excellent, and the inexpensive and practical optical component mounting board and mounting board as well as the printed board with a high degree of freedom in wiring design. Can be provided.
[0047]
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an optical component mounting board, a mounting board, and a printed board according to the present invention.
FIG. 2 is an explanatory view showing a manufacturing process of an optical component mounting board.
FIG. 3 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 4 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 5 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 6 is an explanatory view showing a manufacturing process of an optical component mounting board.
FIG. 7 is a tilt view showing a manufacturing process of the optical component mounting board.
FIG. 8 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 9 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 10 is an explanatory diagram showing an optical component mounting board, a mounting board, and a printed board according to the present invention.
FIG. 11 is an explanatory diagram showing an optical component mounting board, a mounting board, and a printed board according to the present invention.
FIG. 12 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 13 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 14 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 15 is an explanatory diagram showing an optical component mounting board, a mounting board, and a printed board according to the present invention.
[Explanation of symbols]
1 ... Glass substrate 2 ... Hole (via hole)
DESCRIPTION OF SYMBOLS 3 ... Light or thermosetting resin 4 ... Lower clad 5 ... Core 6 ... Photoresist 7 ... Mirror 8 ... Upper clad 9 ... Optical wiring layer 10 ... Light Component mounting substrate 11 ... Bump 12 ... Pad 14 ... Optical component 15 ... Electrical component 16 ... Wiring electrode 20 ... Printed substrate 21 ... Electrode 22 ... Electric wiring layer 23 ... Alignment mark

Claims (2)

A step of forming a via hole penetrating the photosensitive glass substrate by exposing the via hole forming portion of the photosensitive glass substrate by ultraviolet irradiation , performing a heat treatment and a development process by acid treatment, and filling the via hole with a resin by the the steps of the first surface and smooth state a second surface opposite to the photosensitive glass substrate, said first via hole is the photosensitive glass substrate which is filling with the resin A step of applying a first optical wiring material to the surface, a step of patterning the first optical wiring material to form a first optical wiring layer having a core and a cladding, a first optical component and a first optical wiring layer a step of the first optical path conversion mirror for coupling of the core optically formed in the first optical wiring layer, the photosensitive glass substrate having the via hole is filling with the resin A step of applying a second optical wiring material on the second surface facing the first surface coated with a first optical wiring material, patterning the second optical wiring material, the second having a core and a cladding Forming an optical wiring layer; forming a second optical path conversion mirror in the second optical wiring layer for optically coupling the second optical component and the core of the second optical wiring layer; Heating the photosensitive glass substrate on which the first optical wiring layer and the second optical wiring layer are formed, and thermally decomposing the resin filled in the via hole; and the first optical wiring layer and the second optical wiring layer the optical wiring layer, forming a through hole at a position corresponding to the via hole, Rutotomoni to deposit the conductor in said via hole and the through-holes by plating, on the first surface of the photosensitive glass substrate The surface of the formed first optical wiring layer, Further, by sufficiently growing the plating so as to protrude from any of the surfaces of the second optical wiring layer formed on the second surface of the photosensitive glass substrate, the first optical wiring layer A pad connected to the first optical component is formed on the surface, or a pad connected to the second optical component is formed on the surface of the second optical wiring layer, and on the surface of the other optical wiring layer. And a step of forming a bump . An optical component mounting substrate manufacturing method comprising: The method for manufacturing a substrate for mounting an optical component according to claim 1, wherein the photosensitive glass substrate includes at least one material selected from the group consisting of Au and CeO 2.

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